Atomically Dispersed Co2 MnN8 Triatomic Sites Anchored in N-Doped Carbon Enabling Efficient Oxygen Reduction Reaction.

ABSTRACT

Atomically dispersed transition metal-nitrogen/carbon (M-N/C) catalysts have emerged as the most promising substitutes to the precious platinum counterparts toward the oxygen reduction reaction (ORR). However, the reported M-N/C catalysts are usually in the form of common M-N4 moieties with only a single metal active site, and they suffer from insufficient activity. Herein, an unusual trinuclear active structure is elaborately developed with a nitrogen-coordinated single Mn atom adjacent to two Co atoms (Co2 MnN8 ) anchored in N-doped carbon as a highly efficient ORR catalyst via adsorption-pyrolysis of a bimetallic zeolitic imidazolate framework precursor. Atomic structural investigations and density functional theory (DFT) calculations reveal that Co2 MnN8 would experience a spontaneous OH binding to form Co2 MnN8 -2OH as the real active site, leading to a single electron-filled state in the d z 2 ${\mathrm{d}}_{{z}^{2}}$ orbital and an optimized binding energy of intermediates. Accordingly, the as-developed Co2 MnN8 /C exhibits an unprecedented ORR activity with a high half-wave potential of 0.912 V and outstanding stability, not only surpassing the Pt/C catalyst but also representing a new record for the Co-based catalyst.